# Chapter 3 Loop and Helical Antenna¶

## 3.1 Directive gain calculation¶

In [7]:
from __future__ import division
import math

#tan(alpha)=s/c;
#helical antenna Gdmax=15NSC^2/lamda^3
c=1;
n=20;
lamda=1;
Gdmax=(15*n*s*(c)**2)/(lamda)**3;
print("The directive gain is %.3f"%Gdmax)

The directive gain is 63.723


## 3.2 HPBW calculation¶

In [8]:
from __future__ import division
import math

#helical antenna
#part a
c=3*10**8;
f=3*10**9;
lamda=c/f;
print("The wavelength is %g m"%lamda);

#part b
n=20;
s=0.03;
c=0.1;
Gdmax=(15*20*0.3*(0.1)**2)/(0.1)**3;
print("The directive gain is %g"%Gdmax);

#part c
HPBW=math.sqrt((0.1)**3/(20*0.03))*520;
print("The half power beamwidth is %g degree"%HPBW)

The wavelength is 0.1 m
The directive gain is 900
The half power beamwidth is 21.2289 degree


In [9]:
from __future__ import division
import math

#loop antenna
r=10;
lamda=100;
A=(math.pi)*r**2;
Rr=31200*(A/lamda**2)**2;
print("The radiation resistance is %g ohm"%Rr);

The radiation resistance is 30.7932 ohm


In [10]:
from __future__ import division
import math

#loop antenna
l=1;
b=1;
A=l*b;
lamda=100;

The radiation resistance is 3.12 ohm